Blood disorder could offer clues for malaria vaccine

[JAKARTA] A team of international scientists has found that a type of hereditary disorder in some communities in South-East Asia and the South-West Pacific protects its sufferers from malaria, a finding that could drive future vaccine design.

Southeast Asian Ovalocytosis (SAO), an inherited disorder in which red blood cells are oval, instead of round, could be a unique human adaptation to resist malaria, according to a paper published in PLOS Medicine this month (5 September).

The mechanism by which SAO protects against malaria is unknown. However, the oval shape of the blood cells could make it harder for the malaria parasite to attach and enter the red blood cells of its host.

The lead researcher, Ivo Mueller from the Walter and Eliza Hall Institute in Australia, and his team hope to find out which protein the parasite uses to bind to SAO cells. If this protein is found, it could be used to develop a malaria vaccine, a goal that has long eluded researchers.

"The impact of have such a vaccine on elimination could be quite substantial, as it is likely that it would not only prevent people getting sick from malaria but that it may actually prevent people from getting infected with P. vivax," Mueller told SciDev.Net.

SAO is found in some populations in Papua New Guinea, Solomon Islands, Vanuatu, and some parts of Indonesia, Madagascar and Malaysia. Infants born with SAO may suffer from anaemia and jaundice. While adults do not show symptoms, the condition may be associated with gallstones, kidney problems and an enlarged spleen.

Mueller and his team genotyped 1,975 children from three age groups in the Madang area of Papua New Guinea, where both Plasmodium vivax malaria and SAO are common.

They analysed the presence of SAO and P. vivax malaria separately to calculate the association of SAO and malaria. They found that SAO was associated with a 50 per cent reduced risk of malaria.

To try to understand how SAO offers protection against malaria, the team also looked at the SAO cell membrane, which could be providing protection against malaria.

Farah Coutrier, a researcher at the Eijkman Institute in Indonesia, said more research on the mechanism of infection is needed, "for vaccine purposes".

Link to full paper in PLOS Medicine

This article has been produced by our South-East Asia desk.